Information processing apparatuses are used in various fields recently, and methods of use are extended in the background of advanced performance of microprocessor, larger capacity of memory and storage apparatus, lower price of apparatuses.
FIG. 17 is a block diagram of a hardware configuration of a conventional information processing apparatus. As shown in the diagram, the conventional information processing apparatus comprises a CPU 1701, a memory 1702, a secondary storage unit 1703, an input unit 1704, and a display unit 1705.
In the information processing apparatus having such configuration, the operation is explained below. First, a user's instruction is given to the input unit 1704. Next, the CPU 1701 processes according to the program stored in the memory 1702 and the instruction from the input unit 1704, and displays the result of processing in the display unit 1705. At this time, the program and data are exchanged among the CPU 1701, memory 1702, and secondary storage unit 1703.
Some of the information processing apparatuses having the display unit are designed to stop output of image by the display unit when a state not manipulated by the user continues for a prescribed time in order to save energy and prevent heat generation. A hardware configuration of such other conventional information processing apparatus is shown in a block diagram in FIG. 18. In FIG. 18, in addition to the composition in FIG. 17, a clock 1801 is provided, and it measures the time until the output of the display unit 1705 is stopped, and when the duration exceeds a specified time, the output of the display unit 1705 is stopped.
In the output stop state of the display unit 1705, when any user manipulation is given from the input unit 1704, the CPU 1701 generates an image to be displayed in the display unit 1705 according to the program stored in the memory 1702, and the display unit 1705 shows the image again.
In such conventional information processing apparatuses, however, since the CPU is required to have a high processing capacity, power consumption is large, and a heat release structure or large power source is needed. In addition, a secondary storage such as FDD, HDD, CD-ROM is often necessary. It results in a large size and a heavy weight, and it is hard to carry in and work.
Further, in an information processing apparatus having a function of stopping the output of the display unit, in order to display again from the image output stopped state, the CPU executes a program and generates image or data to be displayed. As a result, processing for data generation is complicated, and if it is necessary to acquire data through some communication medium, it takes time until the image is restored in the display unit.
Lately, in a mode based on client server model, by operating a data processing function, and a processing function of its display or user manipulation by independent apparatuses (respectively called data processing apparatus and image display apparatus), a system for connecting them by communication is being developed and employed. In this configuration, at the data processing apparatus side, the result processed corresponding to the user manipulation from the image display apparatus side is sent to the image display apparatus as a drawing command, and at the image display apparatus side, an image is generated according to this drawing command and displayed, so that it appears to be operated by one apparatus. In particular, owing to the progress in the wireless technology, the apparatuses are connected by wireless communication, and the portability of the image display apparatus is enhanced.
In such system for connecting the data processing apparatus and image display apparatus by wireless communication, the image display apparatus is easier to use, but the system does not function if the wireless communication fails between the two apparatuses due to trouble.